Machines
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The wheel and axle does not exist in nature - it is an invention of the human brain.
Nobody knows when the wheel and axle was invented, or who first invented it (1). Drawing upon multiple lines of evidence, the earliest wheels were probably constructed about 5,000 BC, and may have been initally used as pottery wheels. Although ancient Mesopotamia is often credited as the inventing civilization, there is also evidence that ancient Europe, India, and China could have been the first to do so. Regardless, the name of the actual person who made the very first wheel is forever buried in ancient history.
Wheels and axles are commonly used in transport - a wheeled vehicle requires substantially less work to move compared with dragging the same weight. The reason for this is that the wheel and axle transfers the frictional work done from the surface of the ground to its bearings, which confers two advantages. First, the sliding distance is reduced for a given distance of travel. Second, the coefficient of friction at the bearings is usually much lower than if an object was dragged along the ground. |
The first use of the wheel and axle may have been in pottery. |
Beyond transport, the wheel and axle is also commonly used in other situations. Perhaps its oldest use dates back thousands of years in the form of the potter's wheel, which is still used to shape clay into round ceramic ware. Many other examples of wheels and axles in use today exist, such as steering wheels, electric fans, revolving doors, and ferris wheels.
Simple Machines
The wheel and axle is an example of a very basic machine, which is a device that utilizes a mechanical advantage to amplify the magnitude of an applied force (2). As classified by Renaissance scientists several hundred years ago, the wheel and axle is actually just one amongst six so-called simple machines - the other five are the ramp, the lever, the wedge, the screw, and the pulley.
The ramp is a flat surface tilted at an angle, with one end higher than the other. Ramps are also used to lift heavy objects. Compared with lifting an object straight up, it requires less force to move it up the ramp, at the cost of an increase in the distance moved.
The lever consists of a rigid rod (beam) pivoted at a fixed hinge (fulcrum). Levers can be used to lift up heavy objects. By exerting a small force over a long distance of the lever, a large force is exerted over a short distance at the other end, which can be used to lift the object.
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The six simple machines. |
The screw is a cylindrical shaft with helical grooves (threads). Screws have many uses, all of which revolve around binding objects together. Screws convert rotational force into linear force - by exerting a small rotational force over a long distance of the thread, a large axial force is exerted at the business end of the screw.
Last but not least, the pulley is essentially a wheel and axle attached to a cable or rope, such as a block and tackle, which is a set of two or more pulleys with a rope threaded between them. One end of the block and tackle is attached to a fixed mounting point and the other end to a moving load, and the number of sections of rope that support the moving load determines the mechanical advantage - for example, two sections of rope would double the distance required to move the load, but make it half as heavy.
Complex and Modern Machines
For a long time, the six simple machines have been regarded as the elementary building blocks of all machines, such that two or more simple machines working together can be classified as a complex machine. An example of a complex machine would be a wheelbarrow, which takes advantage of both the wheel and axle as well as the lever. Another example would be a bicycle, which uses a combination of the wheel and axle, the lever, and the pulley.
Although complex machines are still widely used, modern mechanics has shifted its perspective to viewing any machine as a kinematic chain, which is an assembly of rigid bodies (links), which share connections (joints) with each other (3). The movement of any link is constrained by its joints with other links. The concept of kinematic chains is useful for understanding of a range of additional machine designs, including robotics.
Yet ultimately, no matter how complex, machines remain devices that amplify force. Despite concerns that machines could surpass humanity, machines themselves cannot do this without guidance from an intelligence, which has nothing to do with what it means to be a machine. The brain's intelligence is what allowed humans to become a dominant species on the planet, even as the kinematic chains comprising the human body weakened relative to our primate ancestors. |
Force does not surpass - intelligence does. |
No species has ever succumbed to a less intelligent one, no matter how much force the latter could muster - if we are concerned over our potential extinction, it is not the machines we need to understand, but the nature of intelligence.
And more importantly, wisdom.
Solace.
References
(1) https://en.wikipedia.org/wiki/Wheel.
(2) https://en.wikipedia.org/wiki/Simple_machine.
(3) https://en.wikipedia.org/wiki/Kinematic_chain.
